This application claims the priority benefit of Taiwan application serial no. 87117110, filed Oct. 15, 1998, the fill disclosure of which is incorporated herein by reference.
1. Field of the Invention
This invention relates to handling digitized data, and more particularly, to a method of handling digitized data, such as digitized video data, in a digital information system, such as a personal computer in conjunction with a digital camera, which allows the handling of the digitized data in the digital information system to be more efficiently carried out to help reduce the load on the CPU (central processing unit) of the computer.
2. Description of Related Art
The digital camera has recently become a popular peripheral device for personal computers (PC) due to breakthrough development in digital signal processing (DSP) technologies. To make the digital camera acceptable to the consumers, it must be cheap to purchase and easy to install and use. To achieve these objectives, most manufacturers use standard components to build their digital camera products. For instance, the data communication interface between the digital camera and the PC employs typically a standard data communication interface, such as ECP (Extended Capabilities Port), EPP (Enhanced Parallel Port), or USB (Universal Serial Bus).
Presently, an ECP/EPP interface can provide a data transmission rate of from 5 Mbps to 12 Mbps (megabits per second), while a full-speed USB interface can provide 12 Mbps. However, in the case of transmitting CIF (Common Interchanged Format) formatted video data at 30 frames per second, the required data rate is 352xc3x97288xc3x972xc3x978xc3x9730=48.66048 Mbps. In order to transmit such a great amount of digitized video data over an ECP, EPP, or USB interface, the data should be compressed.
FIG. 1 is a schematic block diagram showing the system configuration of a digital camera used in conjunction with a PC. As shown, the digital camera includes a video unit 10 and a compression unit 20, with the compression unit 20 being coupled via a peripheral communication interface 50, such as an ECP, an EPP, or a USB interface, to a PC 30. The PC 30 is further coupled to a communication network line 60 and a data storage unit 40. The video unit 10 includes a video image sensor 11, a CDS/AGC (Correlation Duplex Sampling and Auto Gain Control) unit 12, an ADC (Analog to Digital Converter) unit 13, and a signal processor 14. The analog video signal captured by the video image sensor 11 is processed successively by the CDS/AGC unit 12, the ADC unit 13, and the signal processor 14 to obtain a set of digitized video data. The digitized video data output from the signal processor 14 are then compressed by the compression unit 20 through a compression process into compressed data of a specific video compression format, which can be either a proprietary video compression format or a standard video compression format such as MPEG, H.261, or H.263. A proprietary video compression format is typically low in compression ratio, whereas a standard video compression format is typically high in compression ratio.
In the case of using a proprietary video compression format, the compressed video data are transferred via the peripheral communication interface 50 to the PC 30. To allow the compressed video data to be displayed and edited, the PC 30 should first perform a decompression process on these data. This decompression process is the inverse of the compression process performed by the compression unit 20. The decompressed video data can be then displayed on the monitor screen (not shown) of the PC 30. Owing to the limitation of the storage capacity of the data storage unit or the limitation of a bandwith of the communication network line, the decompressed video data stored in the data storage unit 40 or transmitted over the communication network line 60 must be again compressed, typically into a high-compression-rate video compression format, such as MPEG, H.261, or H.263. The data storage unit 40 can be either a hard disk, a magnetic tape, a writable optical disc as a CD (compact disc) or DVD a (digital versatile disc), or a flash memory unit.
One drawback to the use of the low-compression-rate proprietary video compression format, however, is that the captured video data from the video unit 10 should undergo a compression-decompression-compression process before they are stored into the data storage unit 40 or transmitted over the communication network line 60, and therefore the subsequently decompressed data from the data storage unit 40 or the communication network line 60 is significantly poor in fidelity. Moreover, since the PC 30 needs to perform many decompression and compression steps, the load on the PC 30 is very heavy, making the overall system performance of the PC 30 low.
In the case of using a high-compression-rate video compression format such as MPEG, H2.261, or H.263, the compressed video data are transferred via the peripheral communication interface 50 to the PC 30. To allow the compressed video data to be displayed and edited, the PC 30 must first perform a decompression process on these data. This decompression process is the inverse of the previous compression process performed by the compression unit 20. The decompressed video data can be then displayed on the monitor screen (not shown) of the PC 30. One advantage of using high-compression-rate video compression format over low-compression-rate one is that the received data from the peripheral communication interface 50 can be directly stored into the data storage unit 40 or transmitted over the communication network line 60 without having to perform an additional compression as in the foregoing case. Therefore, the PC 30 needs to perform just one decompression process to make the received data displayable and editable. The load on the PC 30 is thus reduced. One drawback to the use of high-compression-rate video compression format, however, is that it typically requires a high-end CPU to allow satisfactory processing speed. Moreover, in application, in order to satisfy the limitation of the storage capacity of the data storage unit or the limitation of a bandwith of the communication network line, the video data must be compressed by the compression unit 20 with a high-compression ratio. However, the performance of the decompressed video data becomes poor while being re-decompressed and being shown in the monitor of the personal computer.
It is therefore an objective of the present invention to provide a method for handling digitized data through compression/decompression and utilization in a more efficient manner than the prior art.
In accordance with the foregoing and other objectives of the present invention, a new method is provided for use in a digital information system to handle digitized data through compression/decompression and utilization.
When used to handle digitized video data, the method includes compressing the original digitized video data concurrently into a first set of compressed data through a first compression process and a second set of compressed data through a second compression process. The first compression process has a lower compression ratio than the second compression process. The first and second sets of compressed data via a data transmission interface are transferred to an information processing unit. The first set of compressed data is decompressed through a decompression process to obtain a set of decompressed data representing the original digitized video data for output of the original digitized video data at an output device. The second set of compressed data remains in compressed form for storage into a data storage unit and transmission over a communication network line.
Since the information processing unit needs to perform just a simple decompression process to decompress the low-compression-rate set of compressed data, the overall system efficiency can be increased.
In general, the method of the invention can be used to handle any kind of digitized data. In this case, the method is broadly defined as a method for handling digitized data through compression/decompression and utilization. The method of the invention includes a first step of compressing the original digitized data concurrently into a first set of compressed data through a first compression process and a second set of compressed data through a second compression process. The first compression process has a lower compression ratio than the second compression process. The first and second sets of compressed data are transferred to an information processing unit. The first set of compressed data is decompressed through a decompression process to obtain a set of decompressed data representing the original digitized data for output of the original digitized data to an output device. The second set of compressed data remains in compressed form for storage and further transfer.
The information processing unit needs to perform just a simple decompression process to decompress the low-compression-rate set of compressed data, the overall system efficiency can be increased.